1. Field of the Disclosure
The present invention relates to optical fiber cables. More particularly, the present invention relates to filler rods for the optical fiber cables.
2. Description of Related Art
A loose tube optical fiber cable generally consists of five or more polymeric “buffer tubes” containing between 2 and 144 glass optical fibers twisted around a central strength member. The central member typically consists of either a fiberglass/epoxy composite rod or a steel wire. The central strength member may be beneficially jacketed with a polymeric material to reach the proper size. The cable core is then encased in a protective outer polymeric jacket which is formed by profile extrusion. Other reinforcing or protective materials, such as reinforcing yarns or waterblocking materials, may be included under the outer polymeric jacket.
Packaging the fibers in multiple individual buffer tubes allows end-users to conveniently handle individual tubes during installation, allowing them to only access the fibers needed without disturbing the relatively fragile glass fibers in the other tubes. Using a minimum of five ‘positions’ for the tubes within the cable ensures that the finished cable has a substantially round shape, which is beneficial in spooling, unspooling and installing the optical cable.
There are situations where the end-user desires the benefits of loose tube structure, but requires a relatively low number of optical fibers. An example would be an end user specifying 24 or 48 optical fibers organized into 12 fiber tubes. Typically, when such a reduced count loose tube cable is made, one or more of buffer tubes inside the cable are replaced by filler rods to fill the five positions and maintain a substantially round structure in the finished cable. In many common cable structures, extruded outer jackets are directly applied over the subunit tubes and filler rods. In this process, problems can arise when parts of the filler rods melt and become intermingled with or adhere to the molten cable jacket material during manufacturing. Consequently, there are ongoing efforts to improve the filler rods.